1. Field of the Invention
The present invention relates to a compressor arrangement of any type as it is usually used for the compression of a gaseous medium, particularly air. More specifically, the present invention relates to a compressor arrangement for the compression of a gaseous medium by means of a compressor which is driven by the working side of a heat engine and connected through a line to consuming devices. The driving side of at least one exhaust-driven supercharger is connected to the exhaust side of the heat engine and is connected through a line to the compressor.
2. Description of the Related Art
Mobile units for supplying compressed gas are required for the operation of movable devices which use compressed air and of implements as they are used, for example, in construction.
In view of the fact that natural resources must be used today more responsibly, it is necessary that especially commercial users of large amounts of energy save a portion of the energy by improved efficiencies of the used machines and devices. In the field of compressor technology, many attempts have been made to utilize exhaust heat, either within the process or outside of the process, in order to improve the energy balance and, thus, increase the overall efficiency.
DE-OS 29 12 190 discloses an arrangement for the production of compressed air of the above-described type in which the exhaust side of a multiple lifting cylinder internal combustion engine is connected to the driving side of an exhaust-driven supercharger. Air which has been taken in by the fresh air compressor of the exhaust-driven supercharger and which has been compressed is supplied through an intermediate cooler to the intake side of the internal combustion engine. Following the intermediate cooler, a line branches from the charging line leading to the internal combustion engine which is connected to the intake side of an air compressor, for example, a reciprocating compressor. The pressure line of the air compressor is connected to auxiliary units which in motor vehicles are operated by means of compressed air, such as, vehicle brakes, pneumatic suspension, door openers, etc. As a result of the proposed arrangement, an additional air filter for the air compressor is unnecessary and the thermal load acting on the components of the air compressor is lowered because of the reduction of the final compression temperature.
A method for operating a compressor with an internal combustion engine for the specific production of high-temperature high-pressure gas is known from EP 0 248 640. In this method, the exhaust heat of the internal combustion engine is utilized in an advantageous manner for increasing the temperature of the compressed gas. However, although this method improves the overall efficiency, this manner of operation is limited to the described specific field of application and is useless for compressed gas which is usually cooled.
In addition, DE-OS 31 34 844 discloses a multiple-stage compressor with coolers which are arranged between the individual stages of the compressor and which are integral components of a heat pump. In this case, compression heat produced by the process is converted into externally usable heat. The heat made available in this manner is not intended for internal use. This does improve the energy balance of the compressor arrangement, however, external processes are necessary for utilizing the recovered energy. Accordingly, this known manner of improving the efficiency cannot be used in independent movable compressors of the above-described type.
A structurally very simple solution is disclosed in U.S. Pat. No. 2,849,173. A heat engine, preferably a multiple-cylinder diesel engine, is connected through a coupling to a reciprocating compressor B. A second compressor A is arranged in the exhaust gas line of the engine. The second compressor A has on the drive side thereof a gas turbine. The compressor side is a multiple-stage axial flow compressor whose intake pipe is connected to a cleaning filter. The pressure pipe of the axial flow compressor is connected through a line to the intake side of the reciprocating compressor B. An intermediate cooler is arranged in this connecting line. The compressor stage ranged upstream in this arrangement is an expensive solution because of the presence of the multiple-stage axial flow compressor which, in addition, requires a large mount of space and, for this reason, is not particularly suitable for a mobile unit. Another disadvantage is the arrangement of the additional compressor stage A in front of the main compressor B because a large flow volume must be compressed from a very low initial pressure to a medium pressure. Because of this large flow volume, the compressor part is also large.
Another solution is proposed in U.S. Pat. No. 3,204,859. Also in this proposal, a precompressing compressor stage in the form of an exhaust gas supercharger is arranged in the exhaust gas line of a heat engine. The working side of the heat engine is connected through a shaft to the actual compressor unit. The airflow produced by the precompressing compressor is divided for charging the diesel engine, on the one hand, and to increase the quantity of the compressor, on the other hand. The supply of the precompressed gas takes place an intermediate portion of the compressor. This arrangement has the disadvantage that only a portion of the precompressed air flow is available for the secondary compression. In addition, the supply of air in the intermediate portion poses problems with respect to sealing and design of the machine because the compressor must be designed in the intake area for a small airflow and for a greater airflow for the area extending from the location where the additional supply takes place to the discharge.
An arrangement which includes two exhaust gas superchargers arranged in the intake line of the compressor is known from U.S. Pat. No. 4,563,132. The multiple-cylinder heat engine, for example, a V8 engine is divided into a motor portion and a compressor portion. The two exhaust gas superchargers are located on the drive side in series in the exhaust pipe of the motor, while the compressor sides of the two superchargers are connected parallel. As is the case in the proposal discussed above, the precompressed airflow is divided to the motor and the compressor. The proposed division of a heat engine into a motor portion and a compressor portion has the disadvantage that the two units operate at the same rate of rotation. This makes it impossible to vary the pressure and the quantity delivered. As a rule, such a combination machine is designed for motor operation, so that the compressor side does not have the optimum design.